Long-chain omega-3 fatty acids (LCn-3FA) are important nutrients necessary for maintaining human health from conception to childhood and throughout life. DHA, an important LCn-3FA, is a major component of nerve, brain and eye tissue. DHA has been associated with a variety of human health benefits including the prevention and management of cardiovascular disease in adults, improved visual acuity in infants, management of inflammatory disease in adults and help with attention deficit disorder. Other LCn-3FA that have been shown to have beneficial physiological effects when consumed, include EPA and DPA.
The diets of people in many countries and cultures have been shown to be deficient in LCn-3FA. The American Heart Association recommends the daily consumption of fish or fish oil supplement for adults to achieve a combined DHA and EPA intake of about 900 mg/day. The current mean intake of DHA and EPA (combined) for adults in North America (which includes about one fish serving every 10 days) is approximately 130 mg/day or 14% of the target intake.
LCn-3FAs have been shown to be required nutrients for optimal maturation of visual and cortical function in human infants. Evidence suggests that breast-fed infants exhibit enhanced cognitive development over formula-fed infants, and it has been suggested that the deficiency of LCn-3FA such as DHA in infant formulas and cow's milk may be linked to cognitive development.
To address these issues, it would be desirable to add LCn-3FA and/or sources of LCn-3FA to ingestable formulations. However, several characteristics make the inclusion LCn-3FA in good tasting food a challenge. LCn-3FA such as DHA, EPA, and DPA are typically derived from fatty fish and are often used in the form of fish oil with the attendant flavour and odour being major barriers to use. Additionally, these fatty acids contain multiple conjugated double bonds and, thus, are extremely susceptible to oxidation and rancidity rendering their purification, concentration and storage very difficult As a result, LCn-3FA-containing oil from fish, or in vitro cultured algae, which is subjected to concentration, purification, and anti-oxidation is very costly to produce, further limiting its use.
Various LCn-3FA-containing nutritional supplements have been developed. These are usually provided in a compressed tablet or capsule format. While these supplements do provide health benefits, they are still associated with a fishy flavor. An increasing area of interest is food products such as spreads like margarine, instant powder concentrates, liquid egg preparations and bread-containing LCn-3FA. It has been found, however, that while food products with strong flavors and/or sweetness can significantly mask the unpleasant fishy taste, milder tasting products are unsuitable for this type of enrichment due to poor palatability. In addition, encapsulated oil tends to separate, particularly from liquid products.
Bovine milk and dairy products play an important role in human health and nutrition. The Canada Food Guide recommends the daily consumption of dairy products for people of all ages. Consumption of milk is particularly important for children. In fact, milk is the primary source of fatty acids for children. Thus, it would be desirable to provide LCn-3FA-enhanced dairy products for consumption. However, addition of exogenous fish oil to milk results in a foul taste.
Several attempts have been made to provide milk-like products or other products that contain LCn-3FA.
U.S. Pat. No. 5,976,606 provides a process for producing a DHA-containing tofu or soybean milk drink, or a dry powder thereof that is stable and inexpensive. A DHA-containing fish oil emulsion is prepared by mixing soybean milk with DHA-containing fish oil at a weight ratio of 1:0.2 to 1:1, and stirring the mixture. The soybean milk drink can be produced by further diluting this emulsion with soybean milk to give a predetermined DHA concentration. DHA-containing tofu can be produced by coagulating the soybean milk containing this emulsion with the addition of a coagulant. Since the same soybean milk as the starting material of tofu or soybean milk drink is used as an emulsifying agent, even if DHA is contained at a high concentration, this does not influence the taste or properties of the product. A dry powder can be obtained by freeze-drying, vacuum drying or spray-drying this tofu or soybean milk drink as required.
U.S. Pat. No. 6,428,832 relates to a process for the preparation of a PUFA-containing food, such as an infant formula, in which a composition comprising a PUFA is added at a late stage of the infant formula preparation process. In this way, the PUFA's are minimally exposed to conditions during the process that induce degradation of the PUFA's.
U.S. Pat. No. 6,596,302 provides methods for providing nutrition and for enhancing neurological development of preterm infants. Also disclosed is an improved nutritional composition containing specified amounts of DHA and arachadonic acid (AA), as well as the respective precursors thereof, fatty acids, alpha-linolenic acid (ALA) and linoleic acid (LA). The method involves feeding these nutrient-enriched formulae for an extended feeding regimen, typically until at least 3 months corrected age (CA), preferably to 6 or even 12 months CA.
U.S. Pat. No. 6,727,373 discloses a microbial polyunsaturated fatty acid (PUFA)-containing oil with a high triglyceride content and a high oxidative stability. In addition, a method is described for the recovery of such oil from a microbial biomass derived from a pasteurized fermentation broth, wherein the microbial biomass is subjected to extrusion to form granular particles, dried and the oil then extracted from the dried granules using an appropriate solvent.
United States Patent Application No. 2004/0131727 provides dairy products containing fish-oil originated EPA and/or DHA which exhibits oxidation and emulsification stability. The milk is acidified by addition of an acid, fermented milk, or acidified milk containing any of the milk acidified by addition of an acid and the fermented milk. The acidified milk contains EPA and/or DHA as fish oil, preferably purified fish oil or fish oil containing EPA and/or DHA in an adjusted amount. The acidified milk is produced through an emulsification process. Preferably, the emulsification is performed after a fermentation process of the acidified milk process through a two-stage emulsification process.
United States Patent Application No. 2003/0211221 describes a composition comprising a polyunsaturated fatty acid (PUFA) and a protective fat, wherein the PUFA comprises an omega-3 PUFA, omega-6 PUFA or a combination thereof. The protective fat may be a triacylglycerol containing at least two and preferably three saturated fatty acids, or a functional derivative thereof.
United States Patent Application No. 2004/0265462 provides an infant milk formula having long chain polyunsaturated fatty acids, sialic acids, and cholesterol.
U.S. Pat. No. 6,200,624 describes the use of triglycerides containing fatty ester moieties that include arachidonic acid (AA) and docosahexaenoic acid (DHA) in enteral nutritionals or nutritional supplements. These triglycerides are derived from lipid mixtures which have high levels of sterols and phosphorous. A preferred embodiment of the invention comprises an infant or enteral nutritional that comprises a lipid source derived from egg yolk. The lipid source derived from egg yolk is prepared by transesterification or hydrolysis, subjecting the mixture to distillation, and esterification with glycerin to result in a triglyceride containing the desired fatty acids of AA and DHA and little or no sterols and phosphorus.
Milk fat is synthesized either from FA which are taken up from the blood (60%) or by de novo synthesis in the mammary gland (40%). LC n-3 FAs are not synthesized by ruminant tissues, so the concentration of LCn-3FA in milk is dependent on how much is ingested (from the diet) and on the amount that flows out of the rumen unaltered. The rumen, however, is a site of intense microbial lipid metabolism. Under normal conditions, unsaturated FAs like LC n-3 FAs are hydrogenated by the rumen microbial population via a process called biohydrogenation. This results in a very low level of LC n-3 FAs reaching the small intestine where they can be absorbed.
During the various steps of lipid biohydrogenation (hydrolysis, isomerization and hydrogenation) in the rumen, numerous intermediate compounds are produced. Research has shown that some FA isomers (e.g. trans-10, cis-12 CLA) can cause significant milk fat depressions (up to 25% reduction) even when small amounts reach the small intestine. The presence of certain FA in the mammary gland is thought to interfere with enzymes (Acetyl CoA carboxylase, fatty acid synthase, stearolyl CoA desaturase) involved in de novo fatty acid synthesis. Thus, the problem of getting milk enriched for LC n-3 FAs without causing a significant decrease in total milk fat levels is not easily solved.
U.S. Pat. No. 5,932,257 describes a feed additive, for milk-producing livestock such as cows, comprising a source of DHA and an inhibitor of microbial degradation of DHA in the rumen comprising feathermeal. While administration of this feed additive to cattle results in a milk product that contains DHA, greater levels of DHA in milk are desirable
Accordingly, despite the foregoing, there remains a need to develop a food product comprising elevated levels of one or more long-chain omega-3 fatty acids.